Re: [PATCH 2/6] KVM: arm64: Remove internal accessor helpers for id regs

Oliver Upton
2022-08-30T17:48:55Z

Hi Reiji,

On Mon, Aug 29, 2022 at 10:45:09PM -0700, Reiji Watanabe wrote:
> Hi Oliver,
>
> On Wed, Aug 17, 2022 at 2:48 PM Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > The internal accessors are only ever called once. Dump out their
> > contents in the caller.
> >
> > No functional change intended.
> >
> > Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> > ---
> > arch/arm64/kvm/sys_regs.c | 46 ++++++++++-----------------------------
> > 1 file changed, 12 insertions(+), 34 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > index e18efb9211f0..26210f3a0b27 100644
> > --- a/arch/arm64/kvm/sys_regs.c
> > +++ b/arch/arm64/kvm/sys_regs.c
> > @@ -1153,25 +1153,17 @@ static unsigned int raz_visibility(const struct kvm_vcpu *vcpu,
> >
> > /* cpufeature ID register access trap handlers */
> >
> > -static bool __access_id_reg(struct kvm_vcpu *vcpu,
> > - struct sys_reg_params *p,
> > - const struct sys_reg_desc *r,
> > - bool raz)
> > -{
> > - if (p->is_write)
> > - return write_to_read_only(vcpu, p, r);
> > -
> > - p->regval = read_id_reg(vcpu, r, raz);
> > - return true;
> > -}
> > -
> > static bool access_id_reg(struct kvm_vcpu *vcpu,
> > struct sys_reg_params *p,
> > const struct sys_reg_desc *r)
> > {
> > bool raz = sysreg_visible_as_raz(vcpu, r);
> >
> > - return __access_id_reg(vcpu, p, r, raz);
> > + if (p->is_write)
> > + return write_to_read_only(vcpu, p, r);
> > +
> > + p->regval = read_id_reg(vcpu, r, raz);
> > + return true;
> > }
> >
> > /* Visibility overrides for SVE-specific control registers */
> > @@ -1226,31 +1218,13 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
> > * are stored, and for set_id_reg() we don't allow the effective value
> > * to be changed.
> > */
> > -static int __get_id_reg(const struct kvm_vcpu *vcpu,
> > - const struct sys_reg_desc *rd, u64 *val,
> > - bool raz)
> > -{
> > - *val = read_id_reg(vcpu, rd, raz);
> > - return 0;
> > -}
> > -
> > -static int __set_id_reg(const struct kvm_vcpu *vcpu,
> > - const struct sys_reg_desc *rd, u64 val,
> > - bool raz)
> > -{
> > - /* This is what we mean by invariant: you can't change it. */
> > - if (val != read_id_reg(vcpu, rd, raz))
> > - return -EINVAL;
> > -
> > - return 0;
> > -}
> > -
> > static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> > u64 *val)
> > {
> > bool raz = sysreg_visible_as_raz(vcpu, rd);
> >
> > - return __get_id_reg(vcpu, rd, val, raz);
> > + *val = read_id_reg(vcpu, rd, raz);
> > + return 0;
> > }
> >
> > static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> > @@ -1258,7 +1232,11 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> > {
> > bool raz = sysreg_visible_as_raz(vcpu, rd);
> >
> > - return __set_id_reg(vcpu, rd, val, raz);
> > + /* This is what we mean by invariant: you can't change it. */
> > + if (val != read_id_reg(vcpu, rd, raz))
> > + return -EINVAL;
> > +
> > + return 0;
> > }
>
> I see no reason for read_id_reg() to take raz as an argument.
> Perhaps having read_id_reg() call sysreg_visible_as_raz() instead
> might make those functions even simpler?

Good point, as this patch has done away with caller-specified RAZ. I'll
incorporate that into v2.

--
Best,
Oliver